Peripheral devices with two microcontrollers are used for the failsafe transmission of data via failsafe bus nodes. Such safe peripheral devices generally achieve safety integration level SIL 2 to SIL 3 according to IEC 61508. In the process industry however operationally proven devices without a bus connection are frequently used for safety applications.
The term failsafe according to DIN V VDE 0801 and VDI/VDE 3542 describes the ability of a system to remain in a safe state or to return immediately to a safe state in the event of failure.